During some cardiac surgeries, the heart can be isolated from the circulatory system while the patient is connected to a heart-lung machine (also known as a perfusion machine). The heart-lung machine provides an extracorporeal circuit to oxygenate and pump blood through the patient's circulatory system. Typically, a venous catheter is inserted into the right atrium and drains blood returning from the body into the extracorporeal circuit of the heart-lung machine. Also, an arterial cannula is inserted into the aorta, so that oxygenated blood from the heart-lung machine can be pumped back into the patient's circulatory system. After these catheters are in place, the aorta may be cross clamped between the arterial cannula and the heart to thereby prevent blood from flowing backwards into the heart. Such a procedure provides oxygenated blood to all areas of the body except the heart. In order to prevent degradation of the heart muscle tissue during the surgery, a cold cardioplegic fluid can be infused into the heart to both cool the heart and stop it from beating. After the initial infusion, the heart may be periodically reperfused to maintain the reduced-temperature, dormant state of the heart.
The cardioplegia solution may be administered in an antegrade manner (through arteries in the normal direction of blood flow), in a retrograde manner (through veins opposite the normal blood flow direction), or in a combination of retrograde and antegrade administration. The cardioplegic solutions can temporarily stop the heart by interfering with the conduction of the heart's natural electric signals that cause heat beats.
Retrograde cardioplegia is conventionally administered by inserting a balloon catheter into the coronary sinus, inflating the balloon, and perfusing the cardioplegic solution backwards through the coronary veins. Some catheters for retrograde coronary sinus perfusion (RCSP) may employ a manually inflating balloon that is filled through an inflation lumen. While the balloon is inflated, the flow of blood or solution from the coronary sinus to the right atrium is blocked.
During the period of time that the heart is deprived of normal blood flow, there is a risk that a portion of the heart muscle tissue may be damaged (such as ischemic heart muscle tissue). Further, after the cardiac surgery in completed and the aorta is unclamped to restore normal blood flow to the heart, the immediate rush of blood through the heart muscle tissue can cause additional damage to the heart muscle tissue to a point that normal blood flow does not return through the ischemic portion of the heart muscle tissue.
Further, in some cases, the heart may be treated without the need for an external blood pump of a heart-lung machine. For example, during a percutaneous coronary intervention, a blockage in a coronary artery may be repaired or removed with a stent or angioplasty balloon that is percutaneously delivered. The blockage in the coronary artery can result in a loss of blood flow through a portion of the heart muscle tissue, thereby creating an area of damaged or ischemic heart muscle tissue.